Every time I hear someone advocating this kind of "convergence", I imagine the dashboard of a Toyota Corolla installed in the cockpit of a 747, or the control panel from a blender transplanted onto an air conditioner.
Why do devices that do different things in different ways need to be interacted with in the same manner?
I came here to say basically the same thing, except you put it much better than I would have. I love the Corolla / 747 comparison. That really gets to the essence of it.
Here's a thought... how about vendors of desktop OS's focus on creating the best possible desktop experience, vendors of tablet OS's focus on creating the best possible tablet experience, etc.? And where there's a happy bit of confluence between those two goals, then exploit it - otherwise, embrace difference and make the best experience for the people who are actually using your product at a moment in time, as opposed to the best experience for "people who are using this and people we hypothetically think might also use this, but on a different device"?
I've always had the mindset that Fogbeam Labs would probably not ever get into the OS business, thinking "Red Hat, Canonical and Novell do a good enough job as Linux vendors" but I swear, sometimes, I find myself wishing we had the resources to throw at a desktop Linux distro.
The problem is some are trying to use the exact same interface everywhere, and that can be a problem. It could work well enough on one type of device, but be very frustrating on another.
I'm not sure which category Ubuntu represents yet, because while the article says one interface, from the videos I've seen Ubuntu Touch kind of has its own UI. The only thing that is exactly the same is the icon bar.
These are very different devices, and yet they use the same interface, meaning that you don't think about what you want to do, you just do it.
For MOST people, that same mentality can scale upto their desktop, onto their television, etc. etc.